An optical pickup device which reproduces information from an optical disc such as a CD (compact disc) as an optical disc is known. The optical pickup device of this type has an optical pickup 111 for reproducing information from an optical disc, a moving mechanism 112 for moving the optical pickup 111 in the radial direction of the optical disc, and a chassis 113 for movably supporting the optical pickup 111 and also supporting the moving mechanism 112, as shown in FIG. 1.
The optical pickup 111 is provided movably in the directions of arrows b1 and b2 in FIG. 1, in an aperture 116 for movement provided in the chassis 113, as shown in FIG. 1. The optical pickup 111 has an optical system (not shown) having an objective lens 118, a driving portion (not shown) for driving and displacing the objective lens 118 in the direction of the optical axis of the objective lens 118 and in the direction orthogonal to the optical axis, and a cover member 120 for covering the driving portion.
The optical pickup 111 has a light source such as a laser diode for emitting a laser beam, a group of lenses constituting the optical system, and a light receiving section for receiving a reflected light from the optical disc, though not shown in the drawing. The driving section provided in the optical pickup 111 has a lens holder for holding the objective lens 118, a supporting mechanism for supporting the lens holder displaceably in the direction of the optical axis of the objective lens 118 and in the direction orthogonal to the optical axis, and an electromagnetic circuit section for driving the lens holder by an electromagnetic force. The cover member 120 is made of, for example, a resin material formed in a substantially box-like shape, and has a substantially elliptic aperture 121 provided therein for exposing the objective lens 118 to the optical disc, as shown in FIG. 1.
The moving mechanism 112 has a supporting base 123 for supporting the optical pickup 111, a supporting shaft 124 for supporting the supporting base 123 movably in the radial direction of the optical disc, a guide portion 125 for movably guiding the supporting base 123, a slide member 126 for moving the supporting base 123, a compression coil spring 127 for energizing the slide member 126 in the axial direction of the supporting shaft 124 with respect to the supporting base 123, a driving gear 128 for driving the slide member 126, and a driving motor (not shown) for rotationally driving the driving gear 128, as shown in FIG. 1.
The optical pickup 111 is arranged on the major surface of the supporting base 123, and the supporting base 123 has bearing portions 131, 131 through which the supporting shaft 124 is movably inserted and a guide recess portion 132 which is movably engaged with the guide portion 125, as shown in FIGS. 1 and 2. At one end of the supporting base 123, a rack portion 133 which is meshed and moved with the driving gear 128 is integrally formed.
This rack portion 133 is formed parallel to the axial direction of the supporting shaft 124, as shown in FIG. 1. The rack portion 133 has engagement pawls 135, 135 which are engaged with the slide member 126, and a retaining piece 136 for retaining one end of the compression coil spring 127.
As shown in FIG. 1, the axial direction of the supporting shaft 124 is arranged parallel to the radial direction of the optical disc, across the aperture 116 for movement of the chassis 113, and both ends of the supporting shaft 124 are fixed on the chassis 113 by fixing portions, not shown.
The guide portion 125 is linearly formed by using a resin material and is formed parallel to the axial direction of the supporting shaft 124 along one lateral edge of the aperture 116 for movement of the chassis 113, as shown in FIG. 1. With this guide portion 125, the guide recess portion 132 of the supporting base 123 is movably engaged, as shown in FIG. 2.
The slide member 126 has a rack portion 138 formed parallel to the axial direction of the supporting shaft 124, and this rack portion 138 is shifted by approximately a half cog thickness from he rack portion 133 of the supporting case 123, as shown in FIG. 3. In the slide member 126, engagement holes 140, 140 are formed which are engaged with the engagement pawls 135, 135 of the rack portion 133 of the supporting base 123, as shown in FIG. 1. Moreover, an aperture 141 in which the compression coil spring 127 is arranged is provided substantially at the center of the major surface of the slide member 126, and a retaining piece 142 for retaining the other end of the compression coil spring 127 is formed at one end of the aperture 141.
As shown in FIG. 1, one end of the compression coil spring 127 is retained by the retaining piece 136 of the rack portion 133 of the supporting base 123, and the other end of the compression coil spring 127 is retained by the retaining piece 142 of the slide member 126. Therefore, the compression coil spring 127 energizes, by its elastic force, the slide member 126 in the direction of an arrow b3 parallel to the axial direction of the supporting shaft 124 with respect to the rack portion 133 of the supporting base 123.
In the optical pickup device, in order to prevent attachment of dust and particles to the facing surface of objective lens 118 of the optical pickup 111 which faces the optical disc due to an air current within the device in the reproduction standby state or the like, an opening/closing mechanism 145 is provided which has an opening/closing member 146 provided movably between a closing position for covering the facing surface of the objective lens 118 and an opening position for opening and exposing the facing surface of the objective lens 118 to the optical disc, as shown in FIG. 1.
The opening/closing mechanism 145 has the opening member 146 for opening/closing the facing surface of the objective lens 118, a rotary shaft 147 for rotatably supporting the opening/closing member 146, and a tension coil spring 148 for energizing the opening/closing member 146 to the closing position, as shown in FIGS. 1 and 4.
As shown in FIG. 1, the opening/closing member 146 has an opening/closing portion 151 for opening/closing the aperture 121 of the cover member 120 of the optical pickup 111, a bearing portion 152 for rotatably supporting the rotary shaft 147, a guide portion 153 slidably engaged with the cover member 120 for guiding the opening/closing portion 151, and an operating portion 154 for rotating the opening/closing portion 151 in the directions of arrows c1 and c2 in FIG. 1.
The opening/closing portion 151 is formed in a substantially flat plate-like shape and slides on the upper surface of the cover member 120, thus opening/closing the aperture 121 of the cover member 120. The bearing portion 152 is integrally formed at one end of the opening/closing portion 151 and has a shaft hole in which the rotary shaft 147 is rotatably inserted. The guide portion 153 is formed to have a cross section of a substantially U-shape fallen sideways, and is slidably engaged with a substantially arc-shaped guide piece 155 which is integrally formed to protrude on the outer circumferential portion of the cover member 120. The operating portion 154 is formed at a position where it is exposed to an operating protrusion 156 provided on the chassis 113, on the outer circumferential portion of the bearing portion 152, as shown in FIG. 1. When the optical pickup 111 is moved to the innermost part of the recording area of the optical disc, the operating portion 154 is abutted against the operating protrusion 156 and rotates the bearing portion 152 in the direction of rotation of the rotary shaft 147.
The rotary shaft 147 is provided upright on the supporting base 123 and is rotatably inserted in the shaft hole of the bearing portion 152 of the opening/closing member 146. The tension coil spring 148 has its one end retained by a retaining piece 158 provided on the supporting base 123 and has its other end retained by a retaining piece 159 situated near the bearing portion 152 of the opening/closing member 146, as shown in FIG. 1. The tension coil spring 148 energizes the rack portion 133 of the supporting base 123 and the rack portion 138 of the slide member 126 in the direction for offsetting the backlash with respect to the driving gear 128, and is precisely moved to the supporting base 123 and the slide member 126 by the driving gear 128. That is, in the optical pickup device, since the rack portion 133 of the supporting base 123 and the rack portion 138 of the slide member 126 are energized by the compression coil spring 127 and thus meshed with the driving gear 128, the optical pickup 111 can be moved with high precision.
On the chassis 113, a disc rotational driving mechanism for rotationally driving the optical disc is provided. The disc rotational driving mechanism has a disc table 160 on which the optical disc is set, and a spindle motor (not shown) for rotationally driving the disc table 160, as shown in FIG. 4.
In the optical pickup device constituted as described above, when reproducing information from the optical disc, the supporting base 123 is moved along the supporting shaft 124 and the guide portion 125 by the moving mechanism 112, and the optical pickup 111 is moved in the radial direction of the optical disc.
In the optical pickup device, as shown in FIG. 5, when the optical pickup 111 is moved in the radial direction of the optical disc to the innermost part of the recording area of the optical disc, the operating portion 154 of the opening/closing member 146 is abutted against the operating portion 156 on the chassis 113 and the optical pickup 111 is moved further by a predetermined quantity, thus rotating the opening/closing member 146 in the direction of an arrow c2 against the energizing force of the tension coil spring 148. In the optical pickup device, when the optical pickup 111 is moved to the innermost circle of the optical disc, the opening/closing member 146 is rotated to the closing position to close the aperture 121 of the cover member 120, thus preventing attachment of dust and particles to the facing surface of the objective lens 118, as shown in FIG. 5.
In the optical pickup device, when the optical pickup 111 is moved into a TOC (table of contents) area on the inner side of the recording area, the opening/closing member 146 is rotated to the opening position and the facing surface of the objective lens 118 of the optical pickup 111 is exposed to the optical disc, thus enabling reproduction of information from the optical disc. The optical pickup 111 reproduces information from the optical disc while the opening/closing member 146 is situated to the opening position, as shown in FIG. 4.
Since the opening/closing mechanism 145 for causing the opening/closing member 146 to carry out the opening/closing operation has the rotary shaft 147 and the tension coil spring 148, the above-described conventional optical pickup device has problems that the manufacturing cost is high, that the assembly work is troublesome, and that assembly failure tends to occur.
In the conventional optical pickup device, since the opening/closing member 146 is rotatably provided via the rotary shaft 147, the lever ratio is related to the quantity of rotation near the bearing portion 152 and the quantity of rotation of the opening/closing portion 151.
In the conventional optical pickup device, since the ratio of the quantity of movement of the optical pickup 111 moved when rotating the opening/closing member 146 to the quantity of rotation of the opening/closing member 146 is large, it is difficult to control the opening/closing operation of the opening/closing member 146 in accordance with the movement of the optical pickup 111 by a control circuit or the like.
Therefore, the conventional optical pickup device has a problem that the irregularity of the rotating position of the opening/closing member 146 prevents complete closure of the aperture 121 of the cover member 120. To restrain the irregularity of the opening/closing operation of the opening/closing member 146, the opening/closing mechanism 145 must increase the precision of each of its component parts and therefore the manufacturing cost must be increased.
In the conventional optical pickup device, the unevenness in the assembly precision or the like of the opening/closing mechanism 145 causes slight unevenness in the slide resistance between the guide portion 153 of the opening/closing member 146 and the guide piece 155 of the cover member 120. Since the slide resistance is amplified by the lever ratio, the opening/closing member 146 cannot carry out the opening/closing operation.